Comparison on the selectivity of the first and second attack of selected lithium organyls as nucleophiles on the carbonyls in the bioctahedron complexes M2(μ-PPh2)2(CO)8 (M=Mn, Re). Is there a neighbour group effect for the second attack?

Article abstract of DOI:10.1016/S0022-328X(98)00377-5

In thf solution the bioctahedron complex Re₂(μ-PPh₂)₂(CO)₈ 1 reacts with one equiv of LiR (R=Ph, Me, nBu, tBu) at temperatures between -90 and -50°C to the acyl monoanion Li[Re₂(μ-PPh₂)₂(CO)₇(ax-C(R)O)] 3 and with a second equiv of LiR¹ (R¹=Ph, Me, nBu) at 20°C to the diacyl dianions Li₂[Re₂(μ-PPh₂)₂(CO)₆( ax-C(R)O)(ax-C(R¹)O)] 12 as trans or cis isomers. Both nearly quantitative reaction steps run selectively: First, both lithium nucleophiles attack exclusively axially coordinated carbonyl ligand. Second, the monoanion with R=Ph forms exclusively the cis diacyl dianions (R¹=nBu, Ph). Through this reaction an anchimeric effect was proved. Third, the monoanions with R=nBu, Me react only to the trans diacyl dianions. In general such mono- and dianions have been reacted with O-alkylating agens to the corresponding carbene and dicarbene derivatives (yield 50-70%) to get single crystals for X-ray structure analyses. All products were identified by means of ¹H, ¹P NMR and ν(CO)IR data. Additionally the molecular structures of the Fischer type carbene complexes Re₂(μ-PPh₂)₂(CO)₇(ax-C(tBu)OMe) 5b, cis-Re₂(μ-PPh₂)₂(CO)₆(ax-C(Ph)OEt )₂ 14 and trans-Re₂(μ-PPh₂)₂(CO)₆(ax-C(nBu) OMe)(ax-C(Ph)OMe) 15b are presented. Opposite to 1 affords the homologous dimanganese complex 2 under the same reaction conditions at -50°C with one and two equiv of lithium organyl an unselective nucleophilic addition to axially and equatorially coordinated monoacyl monoanions and diacyl dianions. Our attempts to separate such isomers of the mono- and dianion type as lithium salt led to their decomposition. However, the carbene and dicarbene derivatives Mn₂(μ-PPh₂)₂(CO)₇(ax-C(Ph)OEt) 9ax and trans-Mn₂(μ-PPh₂)₂(CO)₆(ax-C(nBu) OEt)₂ 16 could be crystallized as air-stable, yellow solids. Their molecular structures are presented.

Full text of DOI:10.1016/S0022-328X(98)00377-5

Journal of Organometallic Chemistry 558 (1998) 81–89
Comparison on the selectivity of the first and second attack of selected
lithium organyls as nucleophiles on the carbonyls in the bioctahedron
complexes M2(v-PPh2)2(CO)8 (M=Mn, Re). Is there a neighbour
group effect for the second attack?
H.-J. Haupt *, D. Petters, U. Flo¨rke
Anorganische und Analytische Chemie der Uni6ersita¨t-GH Paderborn, Fachbereich 13, Chemie und Chemietechnik, Warburger Straße 100,
D-33098, Paderborn, Germany
Received 12 September 1997; received in revised form 26 November 1997
Abstract
In thf solution the bioctahedron complex Re2(v-PPh2)2(CO)8 1 reacts with one equiv of LiR (R=Ph, Me, nBu, tBu) at
temperatures between −90 and −50°C to the acyl monoanion Li[Re2(v-PPh2)2(CO)7(ax-C(R)O)] 3 and with a second equiv of
LiR1 (R1=Ph, Me, nBu) at 20°C to the diacyl dianions Li2[Re2(v-PPh2)2(CO)6(ax-C(R)O)(ax-C(R1)O)] 12 as trans or cis isomers.
Both nearly quantitative reaction steps run selectively: First, both lithium nucleophiles attack exclusively axially coordinated
carbonyl ligand. Second, the monoanion with R=Ph forms exclusively the cis diacyl dianions (R1=nBu, Ph). Through this
reaction an anchimeric effect was proved. Third, the monoanions with R=nBu, Me react only to the trans diacyl dianions. In
general such mono- and dianions have been reacted with O-alkylating agens to the corresponding carbene and dicarbene
1
1
derivatives (yield 50–70%) to get single crystals for X-ray structure analyses. All products were identified by means of H, P
NMR and w(CO)IR data. Additionally the molecular structures of the Fischer type carbene complexes Re2(v-PPh2)2(CO)7(ax-
C(tBu)OMe) 5b, cis-Re2(v-PPh2)2(CO)6(ax-C(Ph)OEt)2 14 and trans-Re2(v-PPh2)2(CO)6(ax-C(nBu)OMe)(ax-C(Ph)OMe) 15b are
presented. Opposite to 1 affords the homologous dimanganese complex 2 under the same reaction conditions at −50°C with one
and two equiv of lithium organyl an unselective nucleophilic addition to axially and equatorially coordinated monoacyl
monoanions and diacyl dianions. Our attempts to separate such isomers of the mono- and dianion type as lithium salt led to their
decomposition. However, the carbene and dicarbene derivatives Mn2(v-PPh2)2(CO)7(ax-C(Ph)OEt) 9ax and trans-Mn2(v-
PPh2)2(CO)6(ax-C(nBu)OEt)2 16 could be crystallized as air-stable, yellow solids. Their molecular structures are presented. © 1998
Elsevier Science S.A. All rights reserved.
Keywords: Lithium organyls; Nucleophiles; Bioctahedron complexes
1. Introduction
fragments on a systematic pathway [1,2]. For dinuclear
complexes without a metal–metal bond, e.g. the reac-
tion of Re2(v-PPh2)2(CO)8 1 and one equiv LiR in thf
solution at −90°C, the nucleophilic attack generating
the monoanion with an axially coordinated acyl group
runs also selectively. At room temperature, however,
this anion and one equiv ClAuPPh3 undergo an acyla-
tion reaction of gold(I) in which the acyl gold(I) com-
pound is trapped in Re2(v-PPh2)2(CO)7(ax-OC(R)-
AuPPh3) [3].
Our earlier studies on the reaction of metal–metal
bonded dinuclear group 7 transition metal complexes
M2(v-PPh2)(v-H)(CO)8 (M=Mn, Re) and nucleophiles
LiR (R=aryl, alkyl) allow the generation of mono-
and dianions in a selective preparative route achieving
cluster expansion reactions with cationic complex
* Corresponding author. Fax: +49 5251 603423.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00377-5

82
H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
At the moment our interest in these dinuclear com-
reaction gives a byproduct with R=O(CH2)4OEt. The
adherence of the axial substitution pattern in the bioc-
tahedron is based on the measured 31P NMR data. In
addition the 1H NMR data show that only the Z
isomer of the carbene group is formed. The spectro-
scopic data indicate no E/Z isomerization. These struc-
tural features are confirmed from the molecular
structure of solid 5b (Fig. 1).
plexes M2(v-PPh2)2(CO)8 (M=Re 1, Mn 2) is focused
on the title question of this paper. To get an answer the
monoanions of 1 and 2 were reacted with different
nucleophiles LiR. The nucleophilic attack of the se-
lected lithium organyls which shows no side-reaction
was analyzed by 31P NMR and w(CO) IR data. Al-
though we could not grow single crystals from the
lithium salts, their conversion to the Fischer type car-
bene derivatives [4] provided suitable samples for X-ray
structure determinations which ascertain the position of
the acyl groups. This study is partly parallel to the
earlier synthesis of acyl monoanions as intermediates
from group 7 transition metal (M) decacarbonyls and
lithium organyls [5]. Further elegant synthetic routes
are known [6–11]. With regard to the title question it
must be stated that until now the reaction behaviour of
the acyl monoanions is not investigated. Additionally,
acyl and diacyl anions including the corresponding
carbene and dicarbene derivatives are hitherto un-
known for the twofold diorganophosphido bridged
complexes 1 and 2. Perhaps this kind of complex offers
a future preparative route for regio- and stereoselective
combination with an appropriate compound to gener-
ate allene type systems and, further, may be of interest
for metathesis reactions [12,13]
Opposite to 1, in thf solution the dimanganese com-
plex 2 and one equiv LiR afford at −50°C instead of
−90°C
the
isomeric
products
Li[Mn2(v-
PPh2)2(CO)7)(ax/eq-C(R)O)] (R=Ph 6ax/eq, Me 7ax/
eq, nBu 8ax/eq). The lesser solubility of 2 against that
of 1 demands the higher reaction temperature of −
50°C. Attempts to precipitate the lithium salts triggers
decomposition. Only the subsequent conversion of each
acyl isomer mixture to the monocarbenes generates the
isolable
derivatives
Mn2(v-PPh2)2(CO)7(ax/eq-
C(R)OEt) (R=Ph, 9ax/eq, Me 10ax/eq, nBu 11ax/eq)
Fig. 2. For correct assignment a comparison of the 31P
and 1H NMR data with those of 4a,b was helpful.
Further support results from the spectroscopic data of
the ax-isomer 9ax which crystallizes from a solution of
9ax/eq whereas the other isomer decomposes. The given
assignments are unambiguous (see Section 3, Experi-
mental details) in spite of the presence of the quadruple
1
manganese nuclei in the H and 31P NMR spectra. The
2
missing signal of the JPP coupling frequency in each of
2. Results and discussion
the eq-isomers via low-temperature measurements
down to 233 K in CDCl3 was not detectable. The H
1
2.1. Preparations with M2(v-PPh2)2(CO)8 (M=Re 1,
Mn 2)
NMR data of the ethoxy group agree with the ratio of
the ax/eq isomers: 1/1.4 in 9ax/eq, 7.5/1 in 10ax/eq and
4/1 in 11ax/eq.
As described in the previous paper [3], in thf solution
of 1 the nucleophilic attack of the reagent LiR at
−90°C affords within 15 min the subsequently named
acyl monoanions as lithium salts Li[Re2(v-
PPh2)2(CO)7(ax-C(R)O)] (R=Ph 3a, Me 3b, nBu 3c,
tBu 3d). (Scheme 1, (i)). According to 31P NMR data of
the reaction solutions, the axial attack of R− runs
selectively in all considered reaction systems at least in
the temperature range from −90 to −50°C, but quan-
titatively only for 3a–c. The yield of 3d is distinctly
lower because the stronger nucleophile tBuLi forms a
known byproduct via a thf alkylation reaction [14]. The
lithium salts 3a–d react to the crystalline carbene
derivatives Re2(v-PPh2)2(CO)7(ax-C(R)OEt) (R=Ph
4a, Me 4b) and Re2(v-PPh2)2(CO)7(ax-C(R)OMe) (R=
nBu, 5a, tBu 5b) on the mostly used synthetic route
with the O-alkylating reagents like Me3OBF4 and
Et3OBF4 in a convenient solvent at room temperature
(Scheme 1, (iii)). The use of the weaker O-alkylation
reagent CF3SO3Et needs a more time-consuming reac-
tion process. As a further disadvantage, this leads to a
known competive ring opening process of thf which is
partly coordinated at the lithium cations in 3a–d. The
To examine our idea of a selective nucleophilic attack
for a second equiv of LiR1, it was evident from the
described preparative results that these experiments
should mainly be focused on the dirhenium complexes
3a–d. Already the first experiments showed that in thf
solution each of the denoted monoanions needs at least
room temperature to be attacked by the same nucle-
ophile. A systematic alteration of the residues R and R1
in the nucleophiles for the dianion formation leads to
the following results (Scheme 1, (ii)): First, the nucle-
ophile LiR1 affords exclusively the diaxial attachment
of both acyl groups in the dianions. Second, the
monoanion 3a (R=Ph) forms the cis dianion in the
salts
Li2[cis-Re2(v-PPh2)2-(CO)6(ax-C(Ph)O(ax-
C(R1)O)] (R1=Ph 12a, nBu 12b) as unique reaction
product. Third, the monoanions 3b–d deliver selectively
the trans dianion in the salts Li2[trans-Re2(v-
PPh2)2(CO)6(ax-C(R)O)(ax-C(R1)O] (R=nBu, R1=
nBu 13a, Ph 13b; R=Me, R1=Me 13c, Ph 13d). Each
of the geometrical isomers is separable as an air-stable
yellow salt in nearly quantitative amounts. The ob-
served number of the (CO) IR absorption bands for
the cis dianion is five and three for the trans dianion

H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
83
Scheme 1.
and correspond with group theoretical considerations.
The (CO) IR mode of the acyl group appears at 1540
cm−1 in 13a. Further spectroscopic characterization
The mentioned cis dianions 12a–b are formed in a
kinetically controlled reaction. The contribution of at
least one phenyl group at the v-P atoms in the neigh-
borhood of the axially attached carbonyl ligand in the
phenylacyl monoanion 3a was investigated by reaction
of complex Re2(v-PEt2)2(CO)8 instead of the phenyl
complex 1 with the nucleophiles LiR (R=Ph, nBu)
under the same conditions. These in situ experiments
were accompanied by 31P NMR measurements and
confirmed that, independent on LiR, a molar reaction
ratio of 1:1 results in the salts Li[Re2(v-PEt2)(CO)7(ax-
C(R)O)] (l 31P (THF): R=Ph, −180.5 (s, 2P, v-P);
R=Bu, −179.8 (s, 2P, v-P)) and a reaction ratio of
1:2 always results in the salts trans-Li2[Re2(v-
PEt2)(CO)6(C(Bu)O)(C(Ph)O)] (l 31P (THF) −181.0 (s,
1
was done by means of 31P and H NMR measurements
as given in Experimental details.
The subsequent derivatization of the dianions 12a,
13a, 13b, 13c with two equiv of the corresponding
O-alkylation agens in thf solution at room temperature
gives the dicarbenes as yellow and air-stable solids in
yields of 50–70%: cis-Re2(v-PPh2)2(CO)6(ax-C(Ph)--
OEt)2 14, trans-Re2(v-PPh2)2(CO)6(ax-C(R)OMe)(ax-
C(R1)OMe) (R=R1=nBu 15a, R1=Ph 15b; R=Me,
R1=Ph 15c). These dicarbenes have been identified by
1H and 31P NMR data and X-ray structure analyses
(Figs. 3–5).

84
H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
Fig. 3. Molecular structure of 14 (conformer A) with hydrogen atoms
omitted.
Fig. 1. Molecular structure of 5b with hydrogen atoms omitted.
PPh2)2(CO)6(ax-C(nBu)OEt)2 16 (Fig. 6) precipitates.
2P, v-P). This shows undoubtedly that in 1 a phenyl
ligand of the v-P atom is involved in a transition state
directing the stereoselectivity on the formation of the
cis dianions 12a–b.
The
unidentified
other
dimanganese
product
decomposes.
2.2. Molecular structures of carbenes and dicarbenes
The analogous experiments with the dimanganese
monoanions and LiR1 in the thf solution allow no
separation of dianions. To obtain an isolable dicarbene
derivative, 2 and two equiv nBuLi in thf solution at
room temperature reacted in the first step to a mixture
of the ax/eq-isomeric dianions. Then these intermedi-
ates and two equiv of Et3OBF4 react to a mixture of
dicarbenes in solution from which only trans-Mn2(v-
2.2.1. Carbenes
Re2(v-PPh2)2(CO)7(ax-C(tBu)OMe) 5b. The molecule
(Fig. 1) represents an edge-bridged bioctahedron com-
plex with two diorganophosphido bridges as edges,
seven carbonyl ligands and the axially coordinated car-
bene group. These eight terminal ligands show almost
ecliptic arrangement viewed along the Re···Re vector
with torsion angles ranging from 2.3 to 11.6°. The
central molecular fragment is a four-membered nearly
planar Re2P2 ring with a dihedral angle ReP2/P2Re of
˚
˚
4.1. The nonbonding Re···Re distance of 3.971(2) A is
somewhat enlarged opposed to that of 3.928(1) A in
Re2(v-PPh2)2(CO)8 [15] due to the substitution of one
axial carbonyl group vs the carbene ligand. The result-
˚
ing Re-carbene C5 bond distance of 2.18(3) A is at the
Fig. 4. Superposition of conformeres A (dashed) and B (solid) of 14.
Phenyl groups and hydrogen atoms omitted.
Fig. 2. Molecular structure of 9ax with hydrogen atoms omitted.

H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
85
(Fig. 3). As for the monocarbene structures these lig-
ands show ecliptic arrangement, too. The carbene tor-
sion angles Re–Re–C–O for molecules A and B are
different with 15.0° for A and only 0.5° for B, respec-
tively. Furthermore, the positions of the ethoxy groups
display two different possibilities for avoiding short
non-bonding intramolecular contacts which otherwise
would arise from the sterically unfavourable cis-ar-
rangement of the carbene ligands. In molecule A the
C–C vector of the ethyl group is almost parallel to the
Re–P bond with torsion angle P–Re–C37–C38 of 4.1
and Re–Re–C37–C38 of 41.8. In molecule B the
Re···Re and the C–C vectors are perpendicular with
torsion angle P–Re–C67–C68 of 123.5° and Re–Re–
C67–C68 of 85.6°. Fig. 4 shows the different OEt-
group arrangements for conformeres
A and B.
Additionally, the Re2P2 ring is no longer planar but
folded with an dihedral angle ReP2/P2Re of 10.4° (aver-
age value for A and B). This also allows better stacking
of the carbene ligands, whereas the carbonyl groups 3
and 3a on the opposite side of the Re2P2 ring are not so
sterically demanding. Similar ring folding due to ligand
substitution has been observed earlier [22]. trans-Re2(v-
PPh2)2(CO)6(ax-C(nBu)OMe)(ax-C(Ph)OMe) 15b. In
contrast to 14 this type of geometrical isomer (Fig. 5)
shows no steric crowding due to the anti-position of the
two different carbene ligands. As consequence the
Re2P2 ring is planar with a dihedral angle ReP2/P2Re of
only 0.9°. Again the carbene groups show Z configura-
tion and the torsion angles which indicate their orienta-
Fig. 5. Molecular structure of 15b with hydrogen atoms omitted.
upper limit of reported Re-carbene C distances and
˚
may be compared to that of 2.08(1) A in Re2(CO)9(ax-
˚
C(nBu)OEt) [9], of 2.09(1) A in MnRe(CO)9(ax-
˚
C(Me)OMe)
[7]a,
or
of
2.125(9)
A
in
[(CO)5ReC(C3H6O)]+ [16]. The vector of the carbene
C5–O bond is oriented parallel to the Re···Re direction
with a torsion angle Re1–Re2–C5–O5 of 6.2° and the
orientation of the carbene ligand along the ReꢀC bond
shows Z configuration. Similar geometrical features are
also valid for the molecular structures of the related
tion
parallel
to
the
Re···Re
vector
are
Re1–Re2–C7–O7 7.7° and Re2–Re1–C8–O8 4.9°, re-
spectively. Further bond lengths and angles show no
unexpected features (Table 1) and compare well with
the above discussed geometries as well as with those of
the related compounds trans-Re2(v-PPh2)2(CO)6(ax-
C(nBu)OC4H8Et)2 (U. Flo¨rke, H.-J. Haupt, D. Petters,
unpublished results). and trans-Mn2(v-PPh2)2(CO)6(ax-
C(nBu)OEt)2 16 (Fig. 6). Complex 16 shows similar
molecular geometry as 15b with trans position of the
carbene ligands. The centre of the molecule lies on a
crystallographic inversion centre which implies a planar
Mn2P2 ring. The carbene ligand has again Z configura-
tion, with the C–O bond parallel to the Mn···Mn
vector indicated by the torsion angle Mn–Mn–C4–O4
of 2.9°. The carbene OEt group shows the same perpen-
dicular arrangement relative to the Mn···Mn direction
known from the B conformere of molecule 14 with
torsion angle Mn–Mn–C9–C10 of 85.5°.
monocarbenes
Re2(v-PPh2)2(CO)7(ax-C(nBu)OEt),
Re2(v-PPh2)2(CO)7(ax-C(nProp)OEt) (U. Flo¨rke, H.-J.
Haupt, D. Petters, unpublished results) and the diman-
ganese derivative Mn2(v-PPh2)2(CO)7(ax-C(Ph)OEt)
9ax, shown in Fig. 2. For this latter complex the related
torsion angle Mn2–Mn1–C2–O2 of the carbene ligand
is 10.6° and the Mn2P2 ring shows only slight deviation
from planarity with a dihedral angle MnP2/P2Mn of
˚
1.6°. The Mn–C2 bond length of 1.954(7) A is also in
the upper range of reported Mn-carbene distances [17–
21].
2.2.2. Dicarbenes
cis-Re2(v-PPh2)2(CO)6(ax-C(Ph)OEt)2 14. There are
two independent molecules (A and B) per asymmetric
unit, each lying on a crystallographic twofold axis
which runs vertically through the midpoints of the
Re2P2 planes. Both molecules show as common struc-
tural feature the central Re2P2 ring with each Re atom
connected to three terminal carbonyl ligands and to one
axially coordinated carbene group with Z configuration
2.3. Conclusion
The title question can be enlightened from the exper-
imental results which show that an anchimeric effect
could be proved, for example, by the quantitative con-
version of the phenylacyl monoanion 3a with LiR1

86
H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
Fig. 6. Molecular structure of 16 with hydrogen atoms omitted.
(R1=alkyl, aryl) to the thermodynamically not fa-
voured cis isomers 12a and 12b. At present it can be
stated that one of the factors influencing the formation
of such cis dianions as Li salts is a phenyl group
attached to the v-P atom. Furthermore the dependency
of a Li+ coordination at the phenacyl group can be
excluded. The complete removal of Li+ by an appro-
priate chelate (12-crown-4-ether) maintains the original
selectivity of the second LiR attack. Additional compu-
tational studies show that free rotation of the phenacyl
ligand around the Re–Cacyl bond in monoanion 2a is
hindered from the v-PPh2 groups. A second attack at
the CO ligand cis to the phenacyl residue including the
mentioned contribution of a v-P phenyl ligand may
therefore be supported by either stabilization of a tran-
sition state with intermediate crowding of phenyl
groups or by an electronic effect of the aryl group or
even by both factors. Further elucidation is expected
from preparation of monoanions with other ligands
than phenyl attached to the acyl group.
chased. The compounds M2(v-PPh2)2(CO)8 (M=Mn
[23], M=Re [24]) and Mn2(CO)10 [25] were prepared
according to literature methods.
3.2. Preparation
3.2.1. Carbenes
Re2(v-PPh2)2(CO)7(ax-C(R)OEt) (R=Ph 4a, Me 4b)
and Re2(v-PPh2)2(CO)7(ax-C(R)OMe) (R=nBu 5a,
tBu 5b). According to the preparative procedure in [3],
each salt Li[Re2(v-PPh2)2(CO)7(ax-C(R)O)] (R=Ph 3a,
Me 3b, nBu 3c, tBu 3d) (0.155 mmol) was dissolved in
10 ml CHCl3 and reacted at room temperature with the
equimolar amount of Et3OBF4 or Me3OBF4. After
stirring for 30 min, the products were separated by
column chromatography (neutral Al2O3) with CH2Cl2/
n-hexane 1/1 as eluant. There was only one yellow main
fraction which contained the carbenes. The solvent was
removed in vacuo and yellow crystals (yield) remained:
105 mg (65%) 4a, 63 mg (40%) 4b, 100 mg (62%) 5a,
and 90 mg (56%) 5b.
Mn2(v-PPh2)2(CO)7(ax/eq-C(R)OEt) (R=Ph 9ax/eq,
Me 10ax/eq, nBu 11ax/eq). One equiv of LiR in cyclo-
hexane/ether solution was added at −50°C to 10 ml
thf solution Mn2(v-PPh2)2(CO)8 2 (100.7 mg; 0.155
mmol). On warming up to room temperature, the
colour of the solution changed from yellow via green to
orange. The solvent was removed in vacuo, and the
residue Li[Mn2(v-PPh2)2(CO)7(ax/eq-C(R)O)] (ax/eq
isomer mixture: R=Ph 6ax/eq; Me 7ax/eq; nBu 8ax/
eq) was dissolved in CH2Cl2 with red colour. The
addition of one equiv Et3OBF4 gave within 15 min the
carbene. The products were separated chromatographi-
cally by use of PLC plates (silicagel 60 F254, Merck).
The ratio of the isomers was derived from the 1H NMR
data of the alkoxy group, and the following red crys-
3. Experimental details
All reactions were carried out in solvents free of
oxygen which were dried according to literature meth-
ods, distilled and stored under argon atmosphere. The
reaction products were characterized by (CO) FTIR
spectroscopy (Nicolet P510), H and 31P NMR spec-
1
troscopy (Bruker AMX 300).
3.1. Chemicals
Re2(CO)10, (Acros), NPPCl and HPPh2 (Strem), 1.6
M PhLi, 1.6 M MeLi, 1.6 M BuLi, 1.5 M tBuLi, 1 M
Et3OBF4, Me3OBF4 and CF3SO3Et (Fluka) were pur-

H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
87
talline products remained after evaporation of the sol-
3.2.2. Dicarbenes
Li2[cis-Re2(v-PPh2)2(CO)6(ax-C(R)O)(ax-C(R1)O)]
vents in vacuo (amount): 9ax/eq separated with the
eluant CH2Cl2/n-hexane 1/2, isomer ratio 1/1.4, 54 mg
(46%); 10ax/eq, 1/2, 45 mg (39%); 11ax/eq, CH2Cl2/n-
hexane 1/1 as eluant, 1/1, 70 mg (70%). It was possible
to separate small amounts of the ax-isomer by fraction-
ated crystallization.
(R=Ph, R1=Ph 12a, nBu 12b) and Li2[trans-Re2(v-
PPh2)2(CO)6(ax-C(R)O)(ax-C(R1)O)] (R=nBu, R1=
nBu 13a, Ph 13b; R=Me, R1=Me 13c, Ph 13d) as
precursor complexes. To 10 ml thf solution of Re2(v-
PPh2)2(CO)8 1 (150 mg, 0.155 mmol) one equiv RLi
(R=Ph, Me, nBu) in cyclohexane/ether solution was
added at −90°C. After reaching room temperature a
second equivalent LiR1 (R1=Bu, Ph) was added. The
formation of the lithium salts due to 31P NMR and IR
measurements was quantitative within 15 min. Subse-
quent removing of solvents in vacuo gave yellow
lithium salts containing different amounts of thf.
cis-Re2(v-PPh2)2(CO)6(ax-C(Ph)OEt)2 14. Within 30
min 30 ml CH2Cl2 solution of 12a (0.155 mmol) and
two equiv Et3OBF4 reacted at room temperature to 14.
The precipitate of LiBF4 was filtered off, and the
components of the solution were adsorbed on neutral
Al2O3 as column material. The eluant CH2Cl2 separated
only the product 14, which gave orange crystals (yield
49%).
Table 1
˚
Selected bond distances [A] and angles [°]
5b
Re1–P1
Re1–P2
Re2–P1
Re2–P2
Re2–C5
C5–O5
2.533(6)
2.524(7)
2.523(7)
2.538(6)
2.18(3)
P1–Re1–P2
P1–Re2–P2
Re1–P1–Re2
Re1–P2–Re2
Re2–C5–O5
76.5(2)
76.4(2)
103.5(2)
103.3(2)
112(2)
1.27(3)
C5–C51
Re1···Re2
1.58(4)
3.971(1)
9ax
Mn1–P1
Mn1–P2
Mn2–P1
Mn2–P2
Mn1–C2
C2–O2
2.402(2)
2.379(2)
2.396(2)
2.399(2)
1.954(7)
1.311(7)
1.509(8)
3.731(1)
P1–Mn1–P2
P1–Mn2–P2
Mn1–P1–Mn2
Mn1–P2–Mn2
Mn1–C2–O2
77.75(6)
77.49(6)
102.07(7)
102.65(7)
121.3(4)
trans-Re2(v-PPh2)2(CO)6(ax-C(R)OMe)
C2–C51
Mn1···Mn1
(ax-C(R1)OMe) (R=R1=nBu 15a, R1=Ph 15b;
R=Me, R1=Ph 15c). As described for the cis dirhe-
nium derivatives, each lithium salt 13b–c reacts with
two equiv Me3OBF4 in CH2Cl2 solution within 20 min
at room temperature to the trans dicarbene. For
product separation, the dicarbene and LiBF4 were pre-
cipitated by addition of n-hexane (5 ml). Both products
were filtered off and the dicarbene dissolved in CH2Cl2.
The dicarbenes crystallized as yellow solids (yield 50–
30%).
trans-Mn2(v-PPh2)2(CO)6(ax-C(nBu)OEt)2 16. To 2
dissolved in thf one equiv BuLi in cyclohexane/ether
solution was added at −50°C. After warming up to
−10°C a second equiv BuLi was added. The solvents
were removed in vacuo and the remaining Li salt
reacted in CH2Cl2 solution with two equiv Et3OBF4 at
0°C. Product separation was done by TLC procedure
yielding (33%) orange crystals.
14
Molecule A
Re1–P1
Re1–P1a
Re1–C30
C30–O30
Re1···Re1a
2.527(2)
2.540(2)
2.131(10)
1.312(11)
3.983(1)
P1–Re1–P1a
Re1–P1–Re1a
Re1–C30–O30
75.87(7)
103.65(7)
121.0(7)
Molecule B
Re2–P2
Re2–P2a
Re2–C60
C60–O60
Re2···Re2a
2.539(2)
2.525(2)
2.106(10)
1.344(10)
3.983(1)
P2–Re2–P2a
Re2–P2–Re2a
Re2–C60–O60
75.53(7)
103.73(7)
120.9(6)
15b
Re1–P1
2.531(5)
2.538(4)
P1–Re1–P2
P1–Re2–P2
75.73(14)
75.95(14)
Re1–P2
Re2–P1
Re2–P2
Re1–C8
C8–O8
Re2–C7
C7–O7
C7–C57
C8–C65
Re1···Re2
2.537(4)
2.520(5)
2.12(2)
1.30(2)
2.08(2)
1.31(2)
1.45(2)
1.46(2)
3.994(1)
Re1–P1–Re2
Re1–P2–Re2
Re1–C8–O8
Re2–C7–O7
104.0(2)
104.3(2)
120.3(12)
121.9(12)
Elementary analyses gave satisfactorily results.
3.3. Spectroscopic data
l values 31P NMR-spectra (CDCl3, standard 85%
H3PO4). Dimanganese monoacyl ions as 6ax (thf) −
29.9 (very broad, vb) (s, 2P, v-P), 6eq (thf) −22.4 (vb)
(s, 2P, v-P); 7ax −27.5 (vb) (s, 2P, v-P), 7eq −23.4
(vb) (s, 2P, v-P); 8ax (CD2Cl2) −26.4 (vb) (s, 2P, v-P),
8eq −22.4 (vb) (s, 2P, v-P). Dirhenium diacyl dianions
as lithium salts, cis isomers (s, 2P, v-P); 12a (thf)
−123.2 (s, 2P, v-P), 12b (thf) −122.9; trans isomers (s,
2P, v-P) 13a (thf) −116.3, −111.3 (CD2Cl2), 13b (thf)
16
Mn1–P1
Mn1–P1a
Mn1–C4
C4–O4
2.404(1)
2.414(1)
1.977(4)
1.310(4)
3.793(1)
P1–Mn1–P1a
Mn1–P1–Mn1a
Mn1–C4–O4
76.16(4)
103.84(4)
119.9(3)
Mn1···Mn1a

88
H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
Table 2
Crystal data and refinement details
5b
9ax
14
15b
16
Formula
MW
C37H32O8P2Re2
1038.9
C40H30O8P2Mn2
810.4
C48H40O8P2Re2*CHCl3
1298.5
C44H40O8P2Re2 C44H48O8P2Mn2
1131.1
Monoclinic
P21/c
15.516(3)
16.707(3)
17.164(3)
99.41(2)
4249(2)
4
876.6
Crystal system
Space group
Orthorhombic
P212121
9.624(2)
18.011(4)
21.391(4)
116.75(2)
3708(1)
4
1.861
6.659
2.2–26.1
4105
Monoclinic
P21/n (No. 14)
18.122(4)
11.745(2)
19.153(4)
106.71(1)
3640(1)
4
1.479
0.835
2.1–27.6
8408
Monoclinic
P2/c (No. 13)
21.685(4)
10.763(2)
21.771(4)
107.27(3)
4867(2)
Monoclinic
P21/n (No. 14)
9.391(3)
16.697(5)
13.708(4)
˚
a (A)
˚
b (A)
˚
c (A)
i (°)
V (A )
3
˚
2120(1)
2
Z
4
Dc (g cm−3
)
1.772
5.252
2.1–27.6
11 255
1.768
5.819
2.4–27.6
6397
1.373
0.722
2.4–27.6
4894
v (mm−1
)
q range for data collection
Indep. data
Parameters
436
0.062
0.148
293(2)
470
0.082
0.154
203(2)
579
0.052
0.107
293(2)
509
0.053
0.135
293(2)
256
R[F2\2|(F2)]
0.052
0.171
203(2)
wR[F2]
T(K)
3JHH=7.5 Hz), 7.11–7.60 (m, 20H, PPh); 5b 1.36 (s,
9H, tBu) 3.44 (s, 3H, OMe), 7.1–7.59 (m, 20H, Ph).
trans-Mn2(v-PPh2)2(CO)6(ax-C(nBu)OEt)2 16 0.42 (t,
−114.6 −109.1 (CDCl3), 13c (thf) −116.5, 13d (thf)
−114.5. Dimanganese carbenes. 9ax −36.9 (vb) (s,
1P, v-P), 9eq −39.6 (vb) (s, 1P, v-P), −28.4 (vb) (s,
1P, v-P). 10ax −36.8 (vb) (s, 2P, v-P), 10eq −42.8
(vb) (1, 1P, v-P) (partly coverd by the signal of the ax
isomer), −25.3 (vb) (s, 1P, v-P); 11ax −36.6 (vb) (s,
2P, v-P); 11eq (small amount). Dimanganese dicarbene
trans-Mn2(v-PPh2)2(CO)6(ax-C(nBu)OEt)2 16 −34.8
(s, 2P, v-P). Dirhenium dicarbenes, cis isomer 14 −
129.8 (s, 2P, v-P); trans isomers (s, 2P, v-P) 15a
−126.5, 15b −127.4, 15c −127.7.
3
3
6H, CH3, JHH=7.2 Hz), 0.86 (t, 6H, CH3, JHH=6.9
Hz), 1.24 (m, 4H, CH2), 1.34 (m, 4H, CH2), 2.98 (t,
3
3
4H, CH2, JHH=7.8 Hz), 3.8 (q, 4H, OCH2, JHH
=
7.2 Hz), 7.05–7.7 (m, 20H, Ph). Dirhenium dicarbe-
3
nes. 14 0.72 (t, 6H, CH3, JHH=7.2 Hz), 3.8 (q, 8H,
OCH2, 3JHH=7.2 Hz), 7.03–7.70 (m, 30H, Ph). 15a
3
0.91 (t, 6H, CH3, JHH=7.1 Hz), 1.24 (m, 4H, CH2),
3
1.35 (m, 4H, CH2), 3.08 (t, 4H, CH2, JHH=8.1), 3.24
1
(s, 6H, OCH3); 7.01–7.06 (m, 4H, p-H(Ph)), 7.15–7.20
l values H NMR-spectra (CDCl3, standard TMS).
(m, 8H, H(Ph)), 7.58–7.6 (s(broad), 8H, o-H(Ph)). 15b
0.94 (t, 3H, CH3, JHH=6.9 Hz), 1.27–1.39 (m, 4H,
Dimanganese monoacyl ions 7ax 2.5 (s (broad), 3H,
CH3), 7eq 2.3 (s (broad) 3H, CH3). Dimanganese car-
3
2
benes, 9ax 0.34 (t, 3H, CH3, JHH=7.2 Hz), 3.6 (q,
2CH2), 3.12 (s (broad), 5H, OCH3 and CH2), 3.17 (s,
3H, OCH3), 6.41 (d, 2H, o-H(ꢀC(PH)). 15c 2.68 (s,
3H, CH3), 3.10 (s, 3H, OCH3), 3.14 (s, 3H, OCH3,
3
2H, OCH2, JHH=7.2 Hz), 6.86 (d, 2H, o-H (ꢀ(PPh),
3JHH=7.2 Hz), 7.18–7.88 (m, 23H, Ph); 9eq 1.63 (t,
3
3
3
3H, CH3, JHH=7.1 Hz), 3.99 (q, 2H, OCH2) JHH
=
6.41 (d, 2H, o-H(ꢀCPh), JHH=8.2 Hz).
7.1 Hz), 6.69 (d, 2H, o-H (ꢀCPh), 3JHH=7.0 Hz,
7.18–7.88 (m, 23H, Ph); 10ax 0.4 (t, 3H, CH3(OEt),
3JHH=7.2 Hz), 3.08 (s, 3H, CH3), 3.64 (q, 2H, OCH2,
3JHH=7.2 Hz), 7.17–7.80 (m, 20H, Ph); 10eq 1.49 (t,
IR data for (CO) absorption bands (cm−1): Di-
manganese acylmonoanions as lithium salts. 6ax/6eq
2050 vs, 1998 m, 1980 s, 1959 m, 1928 s, 1911 vs, 1880
s, 1866 sh, 1556 w; 7ax/7eq 2050 vs, 1996 s, 1957 m,
1926 s, 1903 vs, 1888 vs, 1874 sh, 1540 w; 8ax/8eq
2050 vs, 1994 m, 1978 s, 1955 m, 1926 m, 1913 m,
1901 s, 1882 (broad) vs, 1861 sh, 1531 w. Diman-
ganese carbenes: 9ax 2057 s, 2004 vs, 1982 m, 1973 sh,
1940 s, 1914 s; 9eq 2057 vs, 2023 m, 2003 m, 1986 s,
1942 vs; 10ax 2058 vs, 2004 vs, 1984 m, 1969 sh, 1934
s, 1907 vs; 10eq 2052 vs, 2019 vs 1990 m, 1953 m,
1922 s, 1897 m; 11ax 2058 s, 1999 vs, 1980 m, 1979
sh, 1936 s, 1905 s. 16 1982 s, 1920 vs, 1893 vs. Dirhe-
nium dicarbenes: 14 2025 vs, 2005 m, 1949 w, 1934 m,
1909 s; 15a 1999 vs, 1924 s, 1893 vs; 15b 2002 vs, 1928
s, 1901 vs, 1842 sh; 15c 2004 vs, 1928 s, 1899 vs.
3
3H, CH3(OEt), JHH=7.0 Hz), 2.79 (s, 3H, Me), 4.33
(q, 3JHH=7.0 Hz, 2H, OCH2), 7.17–7.80 (m, 20H,
3
Ph); 11ax 0.4 (t, 3H, CH3(OEt), JHH=7.1 Hz), 0.96
(t, 3H, CH3, JHH=6.7 Hz) 3.37 (t, 2H, CH2, JHH
7.8 Hz), 3.6 (q, 2H, OCH2, JHH=7.2 Hz). Dirhenium
3
3
=
3
3
carbenes. 4a 0.26 (t, 3H, CH3, JHH), 3.44 (q, 2H,
OCH2), 3JHH=7.1 Hz), 6.85 (d, 2H, o-H, (Ph),
3JHH=7.2 Hz), 7.06–7.84 (m, 23H, Ph); 4b 0.34 (t,
3
3H, CH3, JHH=7.2 Hz), 2.88 (s, 3H, CH3), 3.51 (q,
3
2H, OCH2, JHH=7.2 Hz), 7.12–7.61 (m, 20H, Ph);
5a 0.98 (t, 3H, CH3, 3JHH=6.6 Hz), 1.45–1.47 (m,
4H, CH2), 3.12 (s, 3H, OCH3), 3.23 (t, 2H, CH2,

H.-J. Haupt et al. / Journal of Organometallic Chemistry 558 (1998) 81–89
89
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3.4. X-ray data collection, structure solution and refine-
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Table 2. Intensities were collected on a Siemens R3m
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˚
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